<template>
  <div class="music-list">
    <div class="back" @click="back">
      <i class="icons icons-back"></i>
    </div>
    <h1 class="title" v-html="name"></h1>
    <div class="bg-image" :style="avatarStyle" ref="bgImage">
      <div class="play-wrapper">
        <div ref="playBtn" v-show="songs.length>0" class="play" @click="random">
          <i class="icon-play"></i>
          <span class="text">随机播放全部</span>
        </div>
      </div>
    </div>
    <div class="bg-layer" ref="layer"></div>
    <scroll :data="songs" @scroll="scroll"
    :listen-scroll="listenScroll" :probe-type="probeType" class="list" ref="list">
        <div class="song-list-wrapper">
            <song-list @select="selectItem" :songs="songs"></song-list>
        </div>
        <div v-show="!songs.length" class="loading-container">
          <loading></loading>
        </div>
    </scroll>
  </div>
</template>

<script type="text/ecmascript-6">
import Scroll from 'base/scroll/scroll'
import Loading from 'base/loading/loading'
import SongList from 'base/song-list/song-list'
import {mapActions} from 'vuex'
import {songDetail, getUrl,checkMusic} from 'api/singer'
import {playlistMixin} from 'common/js/mixin'

const RESERVED_HEIGHT = 40
export default{
    mixins:[playlistMixin],
    components: {
       Scroll,
       SongList,
       Loading
    },
    mounted () {
       this.imageHeight = this.$refs.bgImage.clientHeight
       this.minTransalteY = -this.imageHeight + RESERVED_HEIGHT
       this.$refs.list.$el.style.top = `${this.imageHeight}px`
    },
    data () {
        return {
           scrollY: 0,
           probeType: 3,
           listenScroll: true,
        }
    },
    methods: {
      //mixins playlistMixin混入的公用方法，用于开启播放器后 自动调整当前页面底部高度
      handlePlaylist(playlist) {
        const bottom = playlist.length > 0 ? '60px' : ''
        this.$refs.list.$el.style.bottom = bottom
        this.$refs.list.refresh()
      },
      random() {
       this.randomPlay({
         list: this.songs
       })
      },
      selectItem (item,index) {
        let id = item.id
        // 获取歌曲
        checkMusic(id).then(res => {
          if(res) {
             /*
               全局设置当前播放的歌曲列表（vuex）
                list 为播放器组件 循环，随机列表等操作时需使用到
                index 当前选中歌曲索引 用于定位到当前歌曲
             */
            console.log(this.songs,index)
             this.selectPlay({
              list: this.songs,
              index
            })
          }
        },err => {
          if(err) {
            // 后续将试图利用代理的方式 捕获资源 暂定
            alert('亲爱的，这首歌没有版权呢！')
          }
        })
      },
      scroll(pos) {
        // console.log(pos)
        this.scrollY = pos.y
      },
      back() {
          this.$router.back()
      },
      ...mapActions([
        'selectPlay',
        'randomPlay'
      ])
    },
    created() {
      this.probeType = 3
      this.listenScroll = true
    },
    props: {
        songs: {
            type: Array,
            default: []
        },
        name: {
            type: String,
            default: ''
        },
        avatar: {
            type: String,
            default: ''
        }
    },
    watch: {
        scrollY (newY) {
            /*
                监听滚动 主要做了以下的工作
                1、向上滑动时，动态改变 bgImage 的高度及层级 （这里运用了一个十分取巧的css技巧）
                2、向下滑动时，根据下滑的动作计算对应的scale，控制 bgImage 的缩放
            */
            let translateY = Math.max(this.minTransalteY,newY)
            let scale = 1
            let zIndex = 0
            const percent = Math.abs(newY / this.imageHeight)
            if(newY > 0) {
                scale +=  percent
                zIndex = 10
            }
            this.$refs.layer.style['transform'] = `translate3d(0,${translateY}px,0)`
            if(newY < this.minTransalteY) {
                zIndex = 10
                this.$refs.bgImage.style.paddingTop = 0
                this.$refs.bgImage.style.height = `${RESERVED_HEIGHT}px`
                this.$refs.playBtn.style.display = 'none'
            }else{
                this.$refs.bgImage.style.paddingTop = '70%'
                this.$refs.bgImage.style.height = 0
                this.$refs.playBtn.style.display = ''
            }
            this.$refs.bgImage.style['transform'] = `scale(${scale})`
            this.$refs.bgImage.style.zIndex = zIndex
        }
    },
    computed: {
      avatarStyle() {
        return `background-image:url(${this.avatar})`
      }
    },
}
</script>

<style scoped lang="stylus" rel="stylesheet/stylus">
  @import "~common/stylus/variable"
  @import "~common/stylus/mixin"

  .music-list
    position: fixed
    z-index: 100
    top: 0
    left: 0
    bottom: 0
    right: 0
    background: $color-highlight-background
    .back
      position absolute
      top: 10px
      left: 6px
      z-index: 50
      .icon-back
        display: block
        padding: 10px
        font-size: $font-size-large-x
        color: $color-theme
    .title
      position: absolute
      top: 0
      left: 10%
      z-index: 40
      width: 80%
      no-wrap()
      text-align: center
      line-height: 40px
      font-size: $font-size-large
      color: $color-text
    .bg-image
      position: relative
      width: 100%
      height: 0
      padding-top: 70%
      transform-origin: top
      background-size: cover
      .play-wrapper
        position: absolute
        bottom: 20px
        z-index: 50
        width: 100%
        .play
          box-sizing: border-box
          width: 135px
          padding: 7px 0
          margin: 0 auto
          text-align: center
          border: 1px solid $color-theme
          color: $color-theme
          border-radius: 100px
          font-size: 0
          .icon-play
            display: inline-block
            vertical-align: middle
            margin-right: 6px
            font-size: $font-size-medium-x
          .text
            display: inline-block
            vertical-align: middle
            font-size: $font-size-small
      .filter
        position: absolute
        top: 0
        left: 0
        width: 100%
        height: 100%
        background: rgba(7, 17, 27, 0.4)
    .bg-layer
      position: relative
      height: 100%
      background: #333
    .list
      position: fixed
      top: 0
      bottom: 0
      width: 100%
      .song-list-wrapper
        padding: 20px 30px
        overflow hidden
      .loading-container
        position: absolute
        width: 100%
        top: 50%
        transform: translateY(-50%)
</style>
